2004 English translation of the 1989 Russian language book. This book combines the information regarding biological research conducted in deep-sea trenches by the expeditions of various countries and compiles complete lists of the currently defined animal species that populate the trench depths, with an indication of the vertical and geographical dissemination of each species and the published sources upon which this information was based. Includes a correlation of all these data and detection of the features inherent to both the ultra-abyssal fauna as a whole, and the fauna of individual trenches, as well as the laws governing the distribution of the trench fauna.